The interaction of a gap with a free boundary in a two dimensional dimer system

Let $\ell$ be a fixed vertical lattice line of the unit triangular lattice in the plane, and let \Cal H be the half plane to the left of $\ell$. We consider lozenge tilings of \Cal H that have a triangular gap of side-length two and in which $\ell$ is a free boundary - i.e., tiles are allowed to protrude out half-way across $\ell$. We prove that the correlation function of this gap near the free boundary has asymptotics $\frac{1}{4\pi r}$, $r\to\infty$, where $r$ is the distance from the gap to the free boundary. This parallels the electrostatic phenomenon by which the field of an electric charge near a conductor can be obtained by the method of images.Comment: 34 pages, AmS-Te

Some Findings Concerning Requirements in Agile Methodologies

gile methods have appeared as an attractive alternative to conventional methodologies. These methods try to reduce the time to market and, indirectly, the cost of the product through flexible development and deep customer involvement. The processes related to requirements have been extensively studied in literature, in most cases in the frame of conventional methods. However, conclusions of conventional methodologies could not be necessarily valid for Agile; in some issues, conventional and Agile processes are radically different. As recent surveys report, inadequate project requirements is one of the most conflictive issues in agile approaches and better understanding about this is needed. This paper describes some findings concerning requirements activities in a project developed under an agile methodology. The project intended to evolve an existing product and, therefore, some background information was available. The major difficulties encountered were related to non-functional needs and management of requirements dependencies

N-body simulations of gravitational dynamics

We describe the astrophysical and numerical basis of N-body simulations, both of collisional stellar systems (dense star clusters and galactic centres) and collisionless stellar dynamics (galaxies and large-scale structure). We explain and discuss the state-of-the-art algorithms used for these quite different regimes, attempt to give a fair critique, and point out possible directions of future improvement and development. We briefly touch upon the history of N-body simulations and their most important results.Comment: invited review (28 pages), to appear in European Physics Journal Plu

Measurement of the Charged Multiplicities in b, c and Light Quark Events from Z0 Decays

Average charged multiplicities have been measured separately in $b$, $c$ and light quark ($u,d,s$) events from $Z^0$ decays measured in the SLD experiment. Impact parameters of charged tracks were used to select enriched samples of $b$ and light quark events, and reconstructed charmed mesons were used to select $c$ quark events. We measured the charged multiplicities: $\bar{n}_{uds} = 20.21 \pm 0.10 (\rm{stat.})\pm 0.22(\rm{syst.})$, $\bar{n}_{c} = 21.28 \pm 0.46(\rm{stat.}) ^{+0.41}_{-0.36}(\rm{syst.})$ $\bar{n}_{b} = 23.14 \pm 0.10(\rm{stat.}) ^{+0.38}_{-0.37}(\rm{syst.})$, from which we derived the differences between the total average charged multiplicities of $c$ or $b$ quark events and light quark events: $\Delta \bar{n}_c = 1.07 \pm 0.47(\rm{stat.})^{+0.36}_{-0.30}(\rm{syst.})$ and $\Delta \bar{n}_b = 2.93 \pm 0.14(\rm{stat.})^{+0.30}_{-0.29}(\rm{syst.})$. We compared these measurements with those at lower center-of-mass energies and with perturbative QCD predictions. These combined results are in agreement with the QCD expectations and disfavor the hypothesis of flavor-independent fragmentation.Comment: 19 pages LaTex, 4 EPS figures, to appear in Physics Letters

Wall fluctuation modes and tensor CMB anisotropy in open inflation models

We calculate the spectrum of large angle cosmic microwave background (CMB) anisotropies due to quantum fluctuations of the gravitational wave modes in one-bubble open inflation models. We find the bubble-wall fluctuation modes, which had been thought to exist discretely in previous analyses, are actually contained in the continuous spectrum of gravitational wave modes when the gravitational coupling is correctly taken into account. Then we find that the spectrum of the tensor CMB anisotropy can be decomposed into the part due to the wall fluctuation modes and that due to the usual gravitational wave modes in a way which is almost model-independent, even when the gravitational coupling is strong. We also discuss observational constraints on the model parameters. We find that an appreciable portion of the parameter space is excluded but the remaining allowable region is still wide enough to leave the one-bubble scenario viable.Comment: 12 pages revtex file, 9 postscript figure

Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events

The $B^0$-$\bar B^0$ oscillation frequency has been measured with a sample of 23 million \B\bar B pairs collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we select events in which both B mesons decay semileptonically and use the charge of the leptons to identify the flavor of each B meson. A simultaneous fit to the decay time difference distributions for opposite- and same-sign dilepton events gives $\Delta m_d = 0.493 \pm 0.012{(stat)}\pm 0.009{(syst)}$ ps$^{-1}$.Comment: 7 pages, 1 figure, submitted to Physical Review Letter

Materiality, health informatics and the limits of knowledge production

© IFIP International Federation for Information Processing 2014 Contemporary societies increasingly rely on complex and sophisticated information systems for a wide variety of tasks and, ultimately, knowledge about the world in which we live. Those systems are central to the kinds of problems our systems and sub-systems face such as health and medical diagnosis, treatment and care. While health information systems represent a continuously expanding field of knowledge production, we suggest that they carry forward significant limitations, particularly in their claims to represent human beings as living creatures and in their capacity to critically reflect on the social, cultural and political origins of many forms of data ‘representation’. In this paper we take these ideas and explore them in relation to the way we see healthcare information systems currently functioning. We offer some examples from our own experience in healthcare settings to illustrate how unexamined ideas about individuals, groups and social categories of people continue to influence health information systems and practices as well as their resulting knowledge production. We suggest some ideas for better understanding how and why this still happens and look to a future where the reflexivity of healthcare administration, the healthcare professions and the information sciences might better engage with these issues. There is no denying the role of health informatics in contemporary healthcare systems but their capacity to represent people in those datascapes has a long way to go if the categories they use to describe and analyse human beings are to produce meaningful knowledge about the social world and not simply to replicate past ideologies of those same categories

Age-dependency of the prognostic impact of tumor genomics in localized resectable MYCN non-amplified neuroblastomas Report from the SIOPEN Biology Group on the LNESG Trials

BACKGROUND: Biology based treatment reduction, i.e. surgery alone also in case of not totally resected tumors, was advised in neuroblastoma patients with localized resectable disease without MYCN amplification. However, whether the genomic background of these tumors may influence outcome was unknown and therefore scrutinized in a meta-analysis comprising two prospective therapy studies and a ‘validation’ cohort. PATIENTS AND METHODS: Diagnostic samples were derived from 406 INSS stages 1/2A/2B tumors from three cohorts: LNESGI/II and COG. Genomic data were analyzed in two age groups (cut-off: 18 months) and quality controlled by the SIOPEN Biology Group. RESULTS: In both patient age groups stage 2 tumors led to similarly reduced event-free survival (5y-EFS: 83+3% versus 80+4%), but overall survival was only decreased in patients >18m (5y-OS: 97+1% versus 87+4%; p=0.001). In the latter age subgroup, only tumors with SCA led to relapses, with 11q loss as the strongest marker (5y-EFS: 40+15% versus 89+5%; p18m but not <18m. CONCLUSION: The tumor genomic make-up of resectable non-MYCN amplified stage 2 neuroblastomas has a distinct age-dependent prognostic impact in neuroblastoma patients. While in the younger age group tumors with unfavourable (SCA) and favorable genetics showed relapses, both without worsening OS, in the older age group only tumors with unfavorable genetics led to relapses and decreased OS.N/

Open Universes from Finite Radius Bubbles

The interior of a vacuum bubble in de Sitter space may give an open universe with sufficient homogeneity to agree with observations. Here, previous work by Bucher, Goldhaber and Turok is extended to describe a thin bubble wall with nonzero radius and energy difference across the wall. The vacuum modes present before formation of the bubble propagate into the interior of open universe and the power spectrum of the resulting gauge invariant gravitational potential is calculated. It is found to become scale invariant on small scales, with onset at about the same scale as that found in the zero radius case. There is sensitivity to the radius and energy difference at large scales, but it is expected that they cannot be strongly constrained because of cosmic variance. As the prediction of a scale invariant spectrum is robust with respect to variation of these parameters at small scales, it is a generic feature of the contribution of these modes for these thin wall models.Comment: 15 pages, LaTeX and revtex macros, final version to appear in Physical Review D, typos and minor wording change